**Chapter 1**
The house was quiet except for the low hum of the refrigerator downstairs and the occasional creak of old floorboards. Sheriff Stilinski was on night shift again, which meant the only two people breathing in the Stilinski house at 11:47 p.m. were Stiles and his sister Avery.
Stiles sat at the edge of his bed, elbows on his knees, spinning a lacrosse ball between his palms. He'd given up pretending to research the latest kanima sighting Scott had texted him about. The words on the screen blurred every time he heard Avery's laugh drift down the hallway from her bedroom.
That laugh used to belong to him.
It still did, in a way. Late nights when she couldn't sleep, she'd crawl into his bed like they were kids again, knees knocking, her head on his chest while they whispered stupid theories about whatever new nightmare was stalking Beacon Hills. She'd fall asleep with her fingers twisted in the front of his t-shirt, and Stiles would lie there for hours, heart hammering, breathing in the scent of her shampoo and trying not to move.
Trying not to want.
The floorboards in the hall creaked. Stiles's head snapped up.
Avery appeared in his doorway wearing one of his old lacrosse hoodies that hung loose on her frame and a pair of sleep shorts that should probably be illegal in several states. Her dark hair was up in a messy knot, a few strands sticking to her neck. She looked warm and soft and like she belonged in his room more than anywhere else on the planet.
"Connor just left," she said, leaning against the doorframe. "You didn't have to hide in here the whole time he was over, you know."
"I wasn't hiding. I was… strategically avoiding the dude who says 'based' unironically." Stiles tossed the lacrosse ball onto his desk. "There's a difference."
Avery rolled her eyes, but her mouth curved in that half-smile that always hit him like a punch to the sternum. She pushed off the doorframe and walked straight to his bed, climbing on without asking. She never asked anymore. She just came.
Her knee brushed his thigh as she settled beside him, back against the headboard. "He's not that bad."
"He's not good enough for you."
The words came out too fast, too rough. Avery turned her head to look at him. For a second the air felt too thin.
"You've said that about every guy I've ever dated," she pointed out, voice softer now.
"Because it's true every time."
Avery studied him. Stiles forced himself to hold her gaze even though his pulse was roaring in his ears. She had their dad's eyes—hazel with flecks of gold—but the way she looked at him sometimes made Stiles feel like she could see every filthy, selfish thought he'd ever had about her.
She nudged his shoulder with hers. "You're such a protective asshole."
"Guilty."
She smiled again, smaller this time, and rested her head on his shoulder. The hoodie she wore smelled like her and like him at the same time. Stiles swallowed hard.
They stayed like that for a long minute. Her bare leg pressed against his sweatpants. He could feel the warmth of her skin through the fabric. His hand itched to slide over her thigh, to hook under her knee and pull her into his lap until there wasn't a single inch of space left between them. Instead he kept perfectly still, the way he always did.
"I broke up with him tonight," Avery said quietly.
Stiles's heart stopped.
He turned his head so fast their noses almost brushed. "You what?"
"I ended it." She shrugged like it wasn't monumental. "Things have felt… off for a while. He's nice. He's safe. But every time he kissed me I kept thinking about how it didn't feel like—" She cut herself off, biting her lip.
"Like what?" Stiles asked, voice low.
Avery didn't answer right away. Her fingers traced a pattern on his comforter, dangerously close to his hand. "Doesn't matter."
It mattered. It mattered so much Stiles felt like he might shake apart.
He should have left it there. Should have been a good brother and asked if she was okay, if she wanted ice cream, if she wanted to watch some trash reality show until she fell asleep.
Instead he said, "Tell me what it didn't feel like, Ave."
Her breath hitched. She lifted her head from his shoulder and looked at him—really looked at him. The lamp on his nightstand painted half her face in warm light and left the other half in shadow. Her lips were slightly parted.
"It didn't feel the way it feels when you hug me too long," she whispered.
The words landed between them like a lit match on dry grass.
Stiles forgot how to breathe.
For years he'd carried this thing alone—this ugly, beautiful, all-consuming want that made him hate himself and feel more alive than anything else ever had. He'd told himself she could never feel it back. That the way she sought him out, the way she curled into him, the way she sometimes looked at his mouth when she thought he wasn't paying attention… it was all innocent. Sisterly.
He'd been so fucking wrong.
"Avery…" His voice cracked.
"I know it's wrong," she said, eyes shining. "I know. But I can't keep pretending it doesn't feel like something when I'm with you. It's been like that for a long time, Stiles. Longer than Connor. Longer than any of them."
Stiles's hand moved without permission, sliding up to cup the side of her neck, thumb brushing her jaw. Her skin was fever-hot under his palm. She leaned into the touch like she'd been waiting years for it.
"I love you," he said. The words scraped out of him, raw and honest. "Not like a brother should. I love you so much it's actually ruining me."
Avery made a small wounded sound and surged forward, pressing her forehead to his. Their noses brushed. He could taste her breath.
"I love you too," she whispered against his mouth. "I'm sorry. I'm so sorry, but I do."
The dam broke.
Stiles kissed her like a man who'd been drowning and finally broke the surface. There was nothing careful about it. Years of restraint snapped all at once. He hauled her into his lap, hands sliding under the oversized hoodie to grip bare skin at her waist. Avery gasped into his mouth, fingers threading through his hair, tugging hard enough to sting.
She tasted like mint toothpaste and the strawberry lip gloss she'd been wearing earlier. She tasted like every fantasy he'd ever hated himself for having. Her thighs straddled him perfectly, heat pressed against him through two thin layers of fabric, and Stiles groaned like he'd been stabbed.
"Fuck, Avery—"
"I know," she panted, rolling her hips once, experimentally. "God, Stiles, I know."
He flipped them so fast the bed creaked in protest, pinning her beneath him. Her hair fanned across his pillow. She looked wrecked already—lips swollen, eyes glassy with want. The sight short-circuited every moral thought left in his head.
His hand slid up her ribs, pushing the hoodie higher. "Tell me to stop and I will. Tell me right now."
Avery grabbed the front of his t-shirt and yanked him back down. "Don't you dare stop."
The kiss turned filthy. Tongues and teeth and months—no, years—of pent-up desperation. Stiles's hand found her breast under the hoodie and she arched into him with a broken moan that he immediately wanted to hear again for the rest of his life.
He was hard enough to hurt. When Avery ground up against him, seeking friction, his vision whited out for a second.
He broke the kiss only to drag his mouth down her neck, sucking a mark just below her ear. Mine, the thought roared through him. Not Connor's. Not anyone's. Mine.
Avery's hands slipped under his shirt, nails dragging down his back. "I used to touch myself thinking about you," she confessed in a shaky whisper. "After you'd fall asleep next to me. I felt so guilty but I couldn't stop."
Stiles cursed viciously against her collarbone. "You're going to kill me. You're actually going to kill me."
"Good," she breathed, tugging at his hair until he met her eyes again. "Because I don't want to do this with anyone else. Ever."
The words settled deep in his chest, dark and possessive and perfect.
He kissed her again, slower this time, savoring. Learning the exact sound she made when he caught her bottom lip between his teeth. Learning how her breath stuttered when his thumb brushed over her nipple.
They stayed like that for a long time—kissing, touching, whispering filthy confessions they'd both carried alone for too long. No one went further than that tonight. Not yet. It felt too big, too sacred to rush even though they were both trembling with need.
Eventually Avery curled into his chest, leg thrown over his hip, face tucked against his neck. Stiles held her like she might disappear if he loosened his grip.
"Connor's going to be a problem," she murmured sleepily.
Stiles stared at the ceiling, fingers stroking slowly up and down her spine under the hoodie.
"No," he said, voice calm in a way that would have terrified anyone who really knew him. "He won't. I'll take care of it."
Avery lifted her head just enough to look at him. There was no fear in her eyes. Only trust and something sharper. Something that looked a lot like relief.
"You promise?"
Stiles kissed her forehead, then her temple, then the corner of her mouth.
"I promise, Ave. He's already gone. He just doesn't know it yet."
She settled back against him with a soft sigh, already drifting off. Stiles kept stroking her back long after her breathing evened out, heart thundering with a lethal combination of love and purpose.
Connor had touched what belonged to him.
That mistake was going to be corrected.
Permanently.
(Word count: 2018)